Food effects in paediatric medicines development for products Co-administered with food.

A small amount of food is commonly used to aid administration of medicines to children to improve palatability and/or swallowability. However the impact of this co-administered food on the absorption and subsequent pharmacokinetic profile of the drug is unknown. Existing information on food effects is limited to standard protocols used to evaluate the impact of a high fat meal in an adult population using the adult medication. In the absence of a substantial body of data, there are no specific guidelines available during development of paediatric products relating to low volumes of potentially low calorie food. This paper brings together expertise to consider how the impact of co-administered food can be risk assessed during the development of a paediatric medicine. Two case studies were used to facilitate discussions and seek out commonalities in risk assessing paediatric products; these case studies used model drugs that differed in their solubility, a poorly soluble drug that demonstrated a positive food effect in adults and a highly soluble drug where a negative food effect was observed. For poorly soluble drugs risk assessments are centred upon understanding the impact of food on the in vivo solubility of the drug which requires knowledge of the composition of the food and the volumes present within the paediatric gastrointestinal tract. Further work is required to develop age appropriate in vitro and in silico models that are representative of paediatric populations. For soluble drugs it is more important to understand the mechanisms that may lead to a food effect, this may include interactions with transporters or the impact of the food composition on gastro-intestinal transit or even altered gastric motility. In silico models have the most promise for highly soluble drug products although it is essential that these models reflect the relevant mechanisms involved in potential food effects. The development of appropriate in vitro and in silico tools is limited by the lack of available clinical data that is critical to validate any tool. Further work is required to identify globally acceptable and available vehicles that should be the first option for co-administration with medicines to enable rapid and relevant risk assessment.

Off-label use of antimicrobials in neonates in a tertiary children's hospital.

PURPOSE: Off-label (OL) use of drugs for hospitalized children is very common. OL use occurs especially in the youngest patients, neonates. This study focused on the OL use of antimicrobials in neonates. To our knowledge, only few studies have focused on the prevalence of OL use of antimicrobials in neonates. METHODS: We investigated the OL use of antimicrobials in neonates in a tertiary children's hospital. First, we investigated what were the most consumed OL antimicrobials in defined daily doses according to hospital's registry data from neonatal intensive care unit (NICU) during 2009-2014. Second, we conducted a targeted retrospective study of premature neonates (400-2000 g) with blood culture-positive infections and receiving antimicrobial therapy between 2005 and 2014 (N = 282). The data were obtained from the electronic patient records and from the hospital's electronic infection registry. Statistical analysis was conducted by using a univariate logistic regression model fitted for OL usage. RESULTS: In NICU, 35% (7/20) of antimicrobials used were OL. Eighteen percent (51/282) of premature neonates with blood culture-positive infections received at least one antimicrobial OL. The most commonly used OL antimicrobials in neonates were meropenem 88% (45/51), rifampicin 18% (9/51), and ciprofloxacin 8% (4/51). The odds for OL use were significantly higher the smaller the neonate birth weight was. An increase in birth weight was found to statistically significantly decrease the probability of OL usage (odds ratio = 0.85 for 100 g increase in birth weight, p value <0.001). CONCLUSION: More studies in neonates on especially dosing and pharmacokinetics of antimicrobials are urgently needed.

Evolution of paediatric off-label use after new significant medicines become available for adults: a study on triptans in Finnish children 1994-2007.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: • Off-label use in children is widespread. New medicines lack marketing authorization for paediatric use, even when they represent significant therapeutic advantages and are intended for treatment of conditions common in children. • Until now no information exists on how off-label use in children develops over time after a significant new medicine is approved for adults and what happens when it is later labelled for one paediatric age group. WHAT THIS STUDY ADDS: • Off-label use of a new significant medicine begins in adolescents and extends to younger children with delay. First marketing authorization to adolescents, providing a more child-friendly formulation, results in increase of off-label use in younger children, and has limited effect on total off-label use. AIM: To investigate the evolution of paediatric off-label use after a therapeutically new group of medicines for a common condition becomes available for adults but is labelled for children with a delay of several years. METHODS: Triptans were used as a model, because migraine is common in children, and is the only indication for triptans. Data on all triptan prescriptions 1994-2007 were extracted from the nationwide Finnish Prescription Register. Prescriptions for children were compared over time. RESULTS: Paediatric patients with triptan prescriptions increased from 204 in 1994 to 2618 in 2007. Sumatriptan accounted for 64% of all paediatric triptan prescriptions. When sumatriptan in a nasal formulation was labelled for children ≥ 12 years in 2003, off-label prescribing to younger children (6-11 years) doubled in 2003-2004. Sumatriptan on-label prescriptions increased to 728 adolescents (45% of sumatriptan in the age group) in 2007, but its off-label use continued also to increase to 1119 (61% of paediatric sumatriptan prescriptions) in 2007. In that year 72% of paediatric triptan use was off-label, 28% on-label. CONCLUSIONS: When a new significant medicine becomes available in adults, off-label use in children starts slowly but continues to extend to younger children reaching a market size which is little influenced by late appearance of a labelled product. Paediatric treatment remains dominated by off-label use despite labelling of a product in an age appropriate formulation to the most relevant age group.

Feasibility evaluation of 3 automated cellular drug screening assays on a robotic workstation.

This study presents the implementation and optimization of 3 cell-based assays on a TECAN Genesis workstation-the Caspase-Glo 3/7 and sulforhodamine B (SRB) screening assays and the mechanistic Caco-2 permeability protocol-and evaluates their feasibility for automation. During implementation, the dispensing speed to add drug solutions and fixative trichloroacetic acid and the aspiration speed to remove the supernatant immediately after fixation were optimized. Decontamination steps for cleaning the tips and pipetting tubing were also added. The automated Caspase-Glo 3/7 screen was successfully optimized with Caco-2 cells (Z' 0.7, signal-to-base ratio [S/B] 1.7) but not with DU-145 cells. In contrast, the automated SRB screen was successfully optimized with the DU-145 cells (Z' 0.8, S/B 2.4) but not with the Caco-2 cells (Z' -0.8, S/B 1.4). The automated bidirectional Caco-2 permeability experiments separated successfully low- and high-permeability compounds (Z' 0.8, S/B 84.2) and passive drug permeation from efflux-mediated transport (Z' 0.5, S/B 8.6). Of the assays, the homogeneous Caspase-Glo 3/7 assay benefits the most from automation, but also the heterogeneous SRB assay and Caco-2 permeability experiments gain advantages from automation.

A Caco-2 cell based screening method for compounds interacting with MRP2 efflux protein.

The aim of this work was to develop a screening method for MRP2 efflux substrates using the well-characterized, human-based intestinal Caco-2 cell model as a platform. MRP2 has a significant role in drug absorption and disposition and is known to co-operate with phase II metabolic enzymes. Caco-2 cells grown in a 96-well plate were loaded with non-fluorescent CDCFDA (diacetate ester of 5(6)-carboxy-2',7'-dichlorofluorescein), which is hydrolyzed to fluorescent CDCF by intracellular esterases. De-esterification in Caco-2 was comparable to that in porcine liver esterases. CDCFDA enters the cells passively, while CDCF is effluxed out of the cells by the apically localized MRP2 and/or basolateral MRPs. The method was optimized with regard to several factors. In the concluding protocol, Caco-2 cells are grown on clear 96-well plates for 8 days. The loading conditions were optimized to 10 min incubation with 5 microM CDCFDA. The highest responses were obtained for samples taken at t=30 min. The samples were analyzed in black 96-well plates with a fluorescence plate reader. The Caco-2 based method utilizing the probe pair CDCFDA/CDCF provides a fast screening tool for MRP2 substrates and/or inhibitors, along with compounds having metabolites formed in Caco-2 that interact with MRP2.

The expression of most UDP-glucuronosyltransferases (UGTs) is increased significantly during Caco-2 cell differentiation, whereas UGT1A6 is highly expressed also in undifferentiated cells.

The human colon carcinoma cell line Caco-2 is often used as a model for intestinal drug absorption. To better understand xenobiotic glucuronidation in Caco-2 cells, we have examined the expression levels of different UDP-glucuronosyltransferases (UGTs) in them. The effects of two main factors were investigated, namely, passage number and cell differentiation. Hence, the mRNA levels of 15 human UGTs of subfamilies 1A and 2B were assessed in both undifferentiated and fully differentiated cells at four passage levels: P31, P37, P43, and P49. Quantitative reverse transcriptase-polymerase chain reaction was used to determine the mRNA levels of individual UGTs, and the values were normalized using beta-actin as a reference gene. The results indicate that although passage number in the tested range exerts a mild effect on the expression level of several UGTs, the contribution of cell differentiation is much larger. The expression of nearly all the UGTs that were examined in this study was significantly, sometimes greatly, increased during cell differentiation. UGT1A6 was a distinct exception to this rule, however, because it was already highly expressed in the undifferentiated cells. The mRNA findings were confirmed at the enzyme activity level by measuring the glucuronidation of 1-naphthol, a very good substrate for UGT1A6, as well as estradiol that is not glucuronidated by this enzyme. The results revealed that 1-naphthol glucuronidation activity was high in both the differentiated and undifferentiated cells, whereas estradiol glucuronidation was only detected in the differentiated cells. Thus, Caco-2 cell differentiation plays a major role in UGT expression and ensuing metabolic reactions.

Transport evaluation of salicylic acid and structurally related compounds across Caco-2 cell monolayers and artificial PAMPA membranes.

The purpose of this study was to evaluate passive vs. proton-dependent active transport mechanisms of salicylic acid (SA) and four structurally related anions. Transport was studied across Caco-2 cell monolayers and artificial lipid membranes (PAMPA) under pH-gradient and iso-pH conditions. Kinetic permeability parameters were provided by bidirectional Caco-2 experiments and concentration-dependency measurements. The transport route and putative transporters involved in SA transport were studied using EDTA and several inhibitors. SA and lipophilic 5-chlorosalicylic acid and 2-hydroxy-1-naphthoic acid reached saturation with increasing compound concentration indicating active transport. Permeation of 5-hydroxysalicylic acid and 5-hydroxyisophthalic acid was not saturated indicating passive transport. PAMPA with pure passive diffusion underestimated the transport of SA compared to Caco-2. Opening up the paracellular tight junctions by EDTA did not increase the transport of SA under the pH-gradient conditions confirming the hypothesis of pure transcellular transport of SA. Active transport of SA remained concentration-dependent even without the pH-gradient, and was reduced by the known MCT1 and OATP-B inhibitors and structurally related anions. Overall, several permeability test protocols are needed to obtain a more complete picture of transport properties of salicylic acid and structurally related compounds.

Mechanistic evaluation of factors affecting compound loading into ion-exchange fibers.

Donnan theory was applied to gain mechanistic understanding on the factors affecting drug loading process, compound-fiber affinity and subsequent release from fibrous ion-exchangers. Impact of initial loading solution concentration on fiber occupancy and loading efficiency of compounds were assessed experimentally and theoretically. Relative affinity towards the anion-exchange fibers was studied by dual loading of monovalent salicylic acid and either more lipophilic 3-isopropylsalicylic acid or divalent 5-hydroxyisophthalic acid. The effect of fiber framework on compound binding was evaluated separately for weakly and strongly basic fibers of similar ion-exchange capacities. The results revealed that loading into the ion-exchange fibers can be efficiently adjusted by the concentration of loading solution, leading to improved controllability of drug release from the fiber and minimised drug loss during the loading procedure. Ion-exchange fibers can be utilised successfully in simultaneous delivery of two ionic drugs, which offers a potential drug delivery system for synergistically active drugs. However, physicochemical characteristics of the drug (lipophilicity, valence) and framework of fibrous ion-exchanger affect the relative affinity of the drug towards the fiber, and should not be neglected when selecting appropriate ion-exchange fiber or optimising the external conditions during loading/release. Application of Donnan theory in modelling calculations supported precisely the experimental observations of compound loading (fiber occupancy and loading efficiency).

Cell-polymer interactions of fluorescent polystyrene latex particles coated with thermosensitive poly(N-isopropylacrylamide) and poly(N-vinylcaprolactam) or grafted with poly(ethylene oxide)-macromonomer.

Cell-polymer interactions of thermosensitive poly(N-isopropylacrylamide) (PNIPAM) or poly(N-vinylcaprolactam) (PVCL) coated particles with RAW264.7 macrophages and intestinal Caco-2 cells were evaluated. Nanosized particles were prepared by modifying the surface of fluorescent polystyrene (FPS) particles with the thermosensitive polymer gels or with poly(ethylene oxide) (PEO)-macromonomer grafts. The particles were characterized by IR-spectroscopy for functional groups, light scattering for size distribution and zeta-potential for surface charge. Effects of temperature and polymer coating/grafting on the cellular interactions were evaluated by cell association/uptake and visualized by confocal scanning microscope. PEO and PNIPAM inhibited the polymer-cell contact by steric repulsion, evidenced by weak attachment of the particles. PVCL-coated FPS was adsorbed on the cells more strongly, especially at 37 degrees C, because of more hydrophobic nature at higher temperatures. The results suggest feasibility of the PNIPAM and PVCL for biotechnological/pharmaceutical applications, as the cell-particle interactions may be modified by size, surface charge, hydrophobicity, steric repulsion and temperature.

Effect of cell differentiation and passage number on the expression of efflux proteins in wild type and vinblastine-induced Caco-2 cell lines.

The mRNA level expression of MDR1, MRP1-6, BCRP and CYP3A4 was determined by quantitative PCR in wild type (Caco-2WT) and vinblastine-treated (Caco-2VBL) Caco-2 cells at different passage levels (32-53). Differentiation increased the mRNA levels of MDR1, BCRP and all the MRPs except MRP4. Corresponding mRNA levels were observed in Caco-2WT and Caco-2VBL, except that the expression of MRD1 was higher in Caco-2VBL than in Caco-2WT cells. CYP3A4 was barely detected in either cell line. MDR1 functionality was studied using rhodamine123 and verapamil as a substrate-inhibitor pair. Corresponding to the observed differences in mRNA levels, MDR1 activity was higher in the Caco-2VBL cells. In Caco-2WT, MDR1 functionality was elevated at low passage numbers (32-35) compared to higher ones (49-53). Verapamil inhibited MDR1 efflux except at higher passage Caco-2WT cells, where no MDR1 activity could be observed. The results support the use of Caco-2VBL cells in MDR1 screening. The functional expression is higher than in Caco-2WT and remains consistent across the studied passages without major differences in mRNA levels of other efflux proteins. As both the passage number and the level of cell differentiation affect the expression profile of efflux proteins, short-term cell growth protocols should be evaluated accordingly.

Enhanced in vitro permeation of furosemide loaded into thermally carbonized mesoporous silicon (TCPSi) microparticles.

The combined release and permeation behavior of furosemide loaded into thermally carbonized mesoporous silicon (TCPSi) microparticles was studied in order to evaluate the potential of TCPSi-loading to improve permeation of furosemide, a BCS class IV compound. Permeation was studied across Caco-2 monolayers at pH 5.5, 6.8 and 7.4 from drug solutions and TCPSi particles. TCPSi-loaded furosemide (39% w/w) exhibited improved dissolution from the microparticles with greatly diminished pH dependence. At pH 5.5, where furosemide solubility restricted the amount that could be dissolved in the control solution to less than 30% of the dose contained in the TCPSi particles, the flux of TCPSi-loaded furosemide across Caco-2 monolayers was over fivefold compared to pre-dissolved furosemide. The improved permeation could be confirmed also from dose-corrected (% dose-permeated) results. At pH 6.8 and pH 7.4, where corresponding doses could be used in control solutions, more than fourfold permeability values were obtained with TCPSi-loaded furosemide. Effects on transepithelial electrical resistance (TEER) and mannitol permeability were monitored and suggest that monolayer integrity was not compromised by the drug-loaded TCPSi microparticles. The improved permeation observed from furosemide-loaded TCPSi particles suggests that the high local concentrations provided by the enhanced dissolution properties of TCPSi-loaded furosemide could prove beneficial for absorption.

The effect of valence on the ion-exchange process: theoretical and experimental aspects on compound binding/release.

The effect of valence of mobile counter-ions (extracting electrolytes), mobile co-ions, and drug-like compounds was evaluated on drug binding/release in ion-exchange fibers. The experimental results support the Donnan theory and suggest that incorporation of monovalent salicylic acid (SA) and divalent 5-hydroxyisophthalic acid (di-COOH) into the anion-exchange fibers was attained mainly as a result of electrostatic (ionic) interaction, with additional contribution of non-electrostatic interactions. Increasing the capacity of ion-exchanger increased the molar amount of compound loading. More efficient release of model anions was observed at increasing valence or concentration of the extracting counter-ion. Potency to release the compounds decreased in the order of citrate (-3) > sulfate (-2) > chloride (-1). The valence of co-ions (sodium (+1) vs. calcium (+2)) in the external solution had only a slight effect on the release. Due to dual site binding (two ionized carboxylate groups), the amount of di-COOH bound into the fibers was half of that of monovalent SA. Also the release was significantly reduced, as the electrostatic interaction was stronger in the case of divalent compound. Simulations on the effect of valence on the Donnan potential and theoretical modeling of the release efficiencies by the external ions supported successfully the conclusions above.

Anthranoid laxatives influence the absorption of poorly permeable drugs in human intestinal cell culture model (Caco-2).

Interactions between widely used anthranoid laxatives and other simultaneously administered drugs are not known. In this paper, the influence of rhein, danthron, sennidins A/B, sennosides A/B, and senna leaf infusion was investigated on the permeability of furosemide, ketoprofen, paracetamol, propranolol, verapamil, digoxin, and Rhodamine 123 across Caco-2 monolayers. The effects on monolayer integrity ([(14)C]mannitol permeability, TEER) were also determined. The in vitro absorption of highly permeable drugs was not strongly affected during co-administration of the laxatives. Furosemide permeability was enhanced by rhein and danthron (3.6 and 3.0-fold), which may partly be due to opening of the paracellular spaces and/or effects on active efflux. However, the secretory permeability of digoxin and Rho 123 was not strongly affected by rhein and danthron, suggesting that inhibition of MDR1 was not responsible for the increased permeation of furosemide. The absorptive permeability of digoxin was decreased by rhein and danthron, offering evidence for effects on apical membranes. The effects on monolayer integrity were detectable, but reversible. According to presented experiments, daily use of laxatives with well-absorbing drugs would seem unlikely to affect drug permeability, but the effects on the absorption of poorly permeable drugs cannot be excluded.

Evaluation of cocktail approach to standardise Caco-2 permeability experiments.

The purpose of this study was to investigate the suitability and reliability of n-in-one approach using FDA suggested compounds for standardising Caco-2 permeability experiments. Special attention was paid to the evaluation of rank order correlation and mechanistic insights of compound permeability. Transport studies with antipyrine, metoprolol, ketoprofen, verapamil, hydrochlorothiazide, ranitidine, mannitol and fluorescein were performed in 12- and 24-well formats, as single compounds and in cocktails under iso-pH 7.4 and pH-gradient (pH 5.5 vs. 7.4) conditions. Compounds were quantified using n-in-one LC/MS/MS analysis. The cocktail-dosing proved to be a feasible method to determine the permeability of the Caco-2 cell line and to introduce external standards for permeability tests. Even though sink conditions were lost in cocktail experiments for highly permeable compounds, the rank order of compound permeability and the classification to low and high permeability compounds remained unchanged between single and cocktail studies and permeability values of 12- and 24-well formats were directly comparable. Under pH-gradient conditions the margin between high and low permeability compounds was narrower due to the lower permeability (higher fraction of ionisation) of basic molecules. Of the compounds studied, antipyrine, metoprolol, hydrochlorothiazide and mannitol are suitable for evaluation and standardisation purposes of passive permeability, while fluorescein would function as paracellular marker under iso-pH 7.4. As efflux activity may vary between cell batches, verapamil is a useful marker for P-glycoprotein.

A modification of the Hammett equation for predicting ionisation constants of p-vinyl phenols.

Currently there are several compounds used as drugs or studied as new chemical entities, which have an electron withdrawing group connected to a vinylic double bond in a phenolic or catecholic core structure. These compounds share a common feature--current computational methods utilizing the Hammett type equation for the prediction of ionisation constants fail to give accurate prediction of pK(a)'s for compounds containing the vinylic moiety. The hypothesis was that the effect of electron-withdrawing substituents on the pK(a) of p-vinyl phenols is due to the delocalized electronic structure of these compounds. Thus, this effect should be additive for multiple substituents attached to the vinylic double bond and quantifiable by LFER-based methods. The aim of this study was to produce an improved equation with a reduced tendency to underestimate the effect of the double bond on the ionisation of the phenolic hydroxyl. To this end a set of 19 para-substituted vinyl phenols was used. The ionisation constants were measured potentiometrically, and a training set of 10 compounds was selected to build a regression model (r2 = 0.987 and S.E. = 0.09). The average error with an external test set of six compounds was 0.19 for our model and 1.27 for the ACD-labs 7.0. Thus, we have been able to significantly improve the existing model for prediction of the ionisation constants of substituted p-vinyl phenols.

Effect of ion-exchange fiber structure on the binding and release of model salicylates.

Salicylates were used as model anions to evaluate the effect of the structure (framework and ion-exchange groups) of fibrous anion-exchangers on the extent and mechanism(s) of compound binding and release. Binding was affected by the physicochemical properties of both the salicylates and the ion-exchange fibers. The highest molar amount of binding was obtained with the most lipophilic salicylate (5-chlorosalicylic acid) and the weak base (vinylpyridine) anion-exchange fibers. However, when the ion-exchange capacity was taken into account, higher binding was obtained in fibers of poly(ethylene) framework compared to the viscose-based fibers. The extent of salicylate release into NaCl solution(s) was dependent on the physicochemical characteristics of both the fiber and the bound model salicylate as well as on the amount of extracting ions. With strong base fibers (trimethylammonium), the viscose framework released the salicylates more efficiently than the poly(ethylene) framework. In the case of weak base fibers, the poly(ethylene) framework released the salicylates to a higher extent than the viscose framework. Calculated equilibrium constants (K) of the ion-exchange reactions illustrated that in addition to electrostatic interactions (pure ion-exchange mechanism), non-electrostatic interactions (hydrophobic interactions and/or hydrogen bonding) were also involved. However, the release of the salicylates was efficiently modified by the amount of extracting electrolyte, demonstrating that ion-exchange was the prevalent release mechanism.

A comparison of the effect of medium- vs. long-chain triglycerides on the in vitro solubilization of cholesterol and/or phytosterol into mixed micelles.

Despite clinical evidence of the cholesterol-lowering effects of phytosterols, the exact mechanisms involved are still unclear. Displacement of cholesterol by phytosterols from mixed micelles, which is due to their greater hydrophobicity, is one of the hypotheses for the lumenal effects contributing to the reduction of intestinal cholesterol absorption. In this study a dynamic in vitro lipolysis method was used to examine the solubilization behavior of cholesterol and/or phytosterols during lipolysis to probe the efficacy of cholesterol displacement from mixed micelles by phytosterols. The effects of lipid chain length on sterol solubilization were studied by using microcrystalline suspensions containing 17% phytosterol or cholesterol, formulated in long-chain TG (LCT) and medium-chain TG (MCT). When digesting cholesterol-suspended in LCT, the entire cholesterol dose was incorporated into the micellar phase. For the cholesterol formulation suspended in MCT, 50.3% of the initial dose was recovered in the micelles. Under the respective conditions, we observed lower solubilization of phytosterols than of cholesterol (roughly fourfold). Only 25% of the initial phytosterol dose was solubilized from suspensions formulated with LCT, and 13% was solubilized from MCT formulations. Co-administration of phytosterol and cholesterol suspensions showed a significant reduction of cholesterol solubilization, particularly when dosed in MCT, with approximately 25% of the cholesterol dose solubilized. Insignificant amounts of cholesterol were displaced by phytosterols when cholesterol was presolubilized in the mixed micelles. The results show that, compared with LCT, mixed micelles containing MCT lipolysis products have a reduced solubilizing capacity for cholesterol, which adds to the effectiveness of the phytosterols in displacing cholesterol. This suggests potential benefits of using medium chain length lipids in cholesterol-lowering phytosterol products.

Susceptibility to lipase-mediated digestion reduces the oral bioavailability of danazol after administration as a medium-chain lipid-based microemulsion formulation.

PURPOSE: To investigate the impact of lipidic formulation type on in vitro dispersion and digestion properties and the relationship to oral bioavailability, using danazol as a model lipophilic poorly water-soluble drug. METHODS: Three lipid-based danazol formulations [a long-chain triglyceride solution (LCT-solution) and self-microemulsifying drug delivery systems (SMEDDS) based on long-chain (C18) lipids (LC-SMEDDS) and medium-chain (C8-C10) lipids (MC-SMEDDS)] were administered to fasted beagle dogs and compared with a micronized danazol formulation administered postprandially and in the fasted state. In vitro dispersion and particle size data for the two SMEDDS were compared, and the distribution/solubilization patterns of danazol across the various phases produced during in vitro digestion quantified. RESULTS: The LCT-solution and LC-SMEDDS formulations significantly enhanced the oral bioavailability of danazol when compared to fasted administration of the powder formulation. In contrast, and despite displaying excellent dispersion properties, the MC-SMEDDS resulted in little enhancement in danazol bioavailability. In support of the in vivo findings, in vitro digestion of the medium-chain formulation resulted in significant drug precipitation when compared with the long-chain lipid formulations. CONCLUSIONS: Digestion of microemulsion preconcentrate formulations based on medium-chain lipids may limit in vivo utility when compared with similar formulations based on long chain lipids.

Use of in vitro lipid digestion data to explain the in vivo performance of triglyceride-based oral lipid formulations of poorly water-soluble drugs: studies with halofantrine.

The relative oral bioavailability (BA) of halofantrine base (Hf) was assessed in male beagle dogs after administration of a medium chain triglyceride (MCT), a long chain triglyceride (LCT), and a blended LCT/MCT lipid solution formulation of Hf (Study 1) and after administration of suspensions of Hf base and Hf. HCl in LCT (Study 2). A series of in vitro lipid digestion experiments were also performed in an attempt to clarify the data obtained. In vitro drug solubilization profiles were markedly dependent on the mass of lipid employed in lipid digestion experiments. At high lipid masses ( approximately 25 mg triglyceride/mL), MCT formulations gave maximal benefit, whereas at low lipid concentrations ( approximately 5 mg triglyceride/mL), LCT formulations provided improved solubilization capacity. The in vitro digestion and solubilization data at lower lipid masses were consistent with the in vivo data where the BA of Hf after oral administration of the LCT solution > LCT/MCT blend > MCT solution. The second BA study showed similar, albeit variable, exposure after oral administration of a suspension of Hf base or Hf. HCl in LCT and this trend was broadly consistent with in vitro results. This study demonstrates the potential utility of in vitro digestion models to assess and rank order the in vivo performance of lipid solution and suspension formulations of poorly water-soluble drugs such as Hf.

Drug solubilization behavior during in vitro digestion of simple triglyceride lipid solution formulations.

PURPOSE: The purpose of this study was to characterize the solubilization and precipitation characteristics of a range of poorly water-soluble drugs during digestion of either long-chain or medium-chain triglyceride (TG) lipid formulations. METHODS: TG solution formulations of five selected drugs (griseofulvin, diazepam, danazol, cinnarizine, and halofantrine) were digested in ritro and drug distribution/solubilization behavior in the resulting digests assessed. RESULTS: For the less lipophilic drugs, the mass of drug dissolved in either medium or long-chain TG was low and the drugs partitioned rapidly into the aqueous digestion phase. For the higher log P drugs, drug transfer to the aqueous phase was limited by accumulation in undigested long-chain TG. In contrast, medium-chain TG was digested completely producing a dispersed aqueous phase that was capable, at least in the case of the high log P drugs, of supporting supersaturated drug concentrations. CONCLUSIONS: The solubilization behavior of lipophilic drugs on digestion of simple TG lipid formulations is a function of the lipophilicity of the drug (which dictates the drug dose and the partitioning behavior), the nature of the colloidal phases produced on digestion of the different formulation lipids, and the kinetics of drug transfer between the digesting formulation and the colloidal phases produced.